Ultra Low-Cost Laser Rangefinders Actualized by Neato Robotics

Ultra-Low-Cost Laser Rangefinder Atop Neato Robotics XV-11 Vacuum Cleaner

A commercially-available ultra low-cost laser rangefinder is finally set to hit department store shelves in February!  I'm speaking of the laser rangefinder presented at ICRA 2008 that costs $30 to build (commented on here at Hizook almost one year ago) that sits atop the recently announced Neato Robotics XV-11 vacuum cleaner.   Others have thoroughly discussed the XV-11's competitiveness with iRobot products, the possible patent infringement of iRobots square-front design, and its ability to perform SLAM (Simultaneous Localization and Mapping).  But everyone has glossed over the coolest part:  Forget about Neato's $400 robot, $60 batteries, $30 wheels (etc.)... if made available, sub-$100 laser rangefinders would revolutionize hobby robotics!  Read on for a description of this compelling (future?) component.

Neato sponsored an ICRA 2008 research paper entitled, "A Low-Cost Laser Distance Sensor," that detailed the design of laser rangefinder that costs only $30 to build.  Called the "Revo LDS", it is pictured below.

Low Cost Laser Rangefinder  Low Cost Laser Rangefinder via Triangulation

Unlike the more expensive (many thousands of dollars) laser rangefinders that use time of flight measurements, such as those discussed here and here, the Revo LDS triangulates the distance to an object using a fixed-angle laser pointer and a CMOS imager, with a known baseline between the two.  To quote:

A compact, rigid point-beam triangulation module incorporating laser, imager, and electronics. With a low-cost CMOS imager and a DSP for subpixel interpolation, we get good range resolution out to 6 m with a 5 cm baseline, at a 4 KHz rate. The key insight to the Revo is that high precision is possible with a small baseline, because of the digital image sensor.

A motor spins the unit at 10Hz to give a full 360-degree field of view.  An optical encoder gives 1-degree angular accuracy.  Not exactly Earth-shattering, but simple and low-cost.  An enclosed, robust USB version of this sensor would have broad appeal, and open up the world of hobby robotics to a sensor that is ubiquitous on research robots.  Oh, and  I suppose the XV-11 isn't half-bad either:

I seriously hope that Neato makes the laser rangefinder component available separately, but rumor has it that they have no intention to do so.  At the moment, I am a bit worried about the possibility of litigation due to similarities between the XV-11 and an iRobot patent (see below).  Hopefully they see the light and avoid destructive lawsuits.

Neato Vacuum Cleaner    iRobot Patent

 

While I'm on the topic...  The idea of triangulating distances using lasers and cheap CMOS/CCD imagers is by no means new.  My favorite example is Morgan Quigley's "Borg Scanner" from Stanford's STAIR Lab.  The Borg Scanner performs triangulation along an entire line (plane) simultaneously using the exact same technique.  Scanning a green laser-line across a scene produces dense 3D point clouds.  You can see a few photos and a video of it being used below.  A forthcoming ICRA 2009 paper on the scanner entitled "High-Accuracy 3D Sensing for Mobile Manipulation: Improving Object Detection and Door Opening" is also quite good.  I've heard rumors that design and fabrication details for this sensor is going to be released as "open source"; I am anxious to give it a try.

Borg Scanner Distance Sensor  Borg Scanner Distance Sensor Scan

 

Whether a commercial unit or home-brewed open source initiative, it appears that ultra low-cost laser rangefinders are on the horizon.  Next on the wish-list: low-cost flash LADAR -- perhaps Microsoft's Project Natal will deliver...?

 

Comments

I am wondering if it is a good idea to replace the motor with a line laser. Do you think some people will live with ~45 degrees scope if the module is really cheap?
—sk

@sk

I'm not really sure I follow your question.   Are you referring to the Revo LDS or the Borg Scanner?

—Travis Deyle

I mean Revo LDS. Something like

http://www.seattlerobotics.org/encoder/200110/vision.htm

I wonder why there is no commercialized product like this. Those image sensors in the cell phones and web cameras are high quality and inexpensive. Personally I would like to make such a product...

—sk

@sk

Ah yes, that is exactly how the Borg Scanner operates.  The only difference: they are scanning the line laser around to create full 3D point clouds rather than just a planar scan.

 

—Travis Deyle

Any idea what the part number of their or a similar cmos imager is?  All I gather is that a line is 752 pixels wide, it has a global shutter, minimum exposure time of 35 microseconds, can collect at least 10 lines of data at 4 KHz, and costs south of $30 (at least in quantity). 

Or can most any cmos imager be driven at high frame rates while sacrificing vertical resolution?

Not sure what imager that might be... maybe this guy from Aptina: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=557-144...

I'm not sure what kind of frame rate it could achieve if only ten lines are being read.

i also wonder if its possible to run a normal image sensor at high frame rates with just a few lines resolution

 

the processor neato uses is a bf531 from analog devices - something like srv-1

—Anonymous
Hi It is interesting. Do you know where can I buy this sensor Revo LDS?
—kai

Using a linear array ( Perkin Elmer, Hamamatsu, Aptina ... )  is a simple and cheap way to build a triangulation sensor if you?re only interested in planar mapping ( parallel to the floor in this case ). You can run the array faster and the system is more data efficient than using a 2d imager. A little trig ( or a LUT ) and you?ve got range values at  nearly the  array scan rates.  Rotate sensor and you get a polar map. It?s 30 year old tech but can be a nice package. 

You can do the same with 2D imagers but most won?t let you select lines or ROIs.  You wait for the frame and throw out the data you?re not interested in.  But you can use Walmart parts instead of specialized industrial components and spend your budget on software/processors.   For $30, 2d imaging is probably what they?re using.

Cylindrical optics and a good bandpass filter would help a lot with data reduction in both cases but compensating for low light returns ( scattering, shiny curves, dark things, etc... ) can be a little tricky. 

 Good, fast, cheap... pick two.

From a cleaning perspective, I wonder how you get the thing to clean under the bed and other scanner shadow areas?

 

—Greg

Hi,

I am not sure if my question is exactly relavant. I am looking for 2d range finders with a scanning range of about 10m for planar mapping. An angular accuracy of about 0.5 degree would be apt with a scanning frequency of about 4KHz. I want to use such a range finder to get contours of moving objects(humans, cycles) from a height of about 10 meters.

Till now I could only zero in upon companies like Sick and Reigl. But these scanners are way beyond the budget allocated for my final year project. 

Please reply, if  you know of anything similar which would meet my requirements.

Arigato

—Akhilesh
A modified vacuum robot that uses exactly the same technique as the neato: http://codeninja.de/drfloyd/
—Anonymous
Hi ! The university in our town happens to habe a "flatrate" ieee access, so perhaps you now someone who has too. They do use a cheap cmos imager that is able to select an Area Of Interest, and they choose one line per software (when calibrating the device; further along calibrating the tilt is mechanically removed with an adjust screw etc, then lock-glued.) This enables sub-pixel-interpolation of the position! Do this with some junky cmos cam and I get interested ;) Another thing is: the data rate remains, they read out 10k lines per second! Of course they thought of 3D but found this would waste battery power for data processing (and would not sufficiently improve the situation for the low height chap from its position of view ;) Greetings! Andi.
—Andis

Hi again.

Sorry, did forget to turn on java script, all my formatting wasted ;)

Arigato, are you from USA? If you still need the scanner: please buy a neato xv-11, extract the scanner, do your project, reassemble it and sell it.

Just propose a price (as the buyer will loose warranty, should be something less then 100%)... and if you find a freight by ship say 4weeks that has insurance AND is affordable (less than 80$) I would be interested ;)

There are some other people using the scanner:  http://robotbox.net/blog/gallamine/open-lidar-project-hack-neato-xv-11-lidar-200-bounty

Greetings!

Andi -- reachable by mail form at http://and741.funpic.de/mail.htm

—Andis

The Neato XV-11 laser rangefinder (ie. the commercial version of the RevoLDS) has now been thoroughly hacked.  There are a number of nice tutorials available:

 

Still no word about availability of just the laser rangefinder (as opposed to whole robot).  We'll keep you posted if we hear anything. [Props to the folks at ROS.org

RevoLDS -- The laser rangefinder on the Neato XV-11

 

—Travis Deyle

Hash, who I believe is the guy who first hacked the Neato LRF (and won the prize bounty), has a really great website dedicated almost exclusively (at this point) to the Neato XV-11 Laser rangefinder.

He's done some great teardowns in the past (eg. of the wheel hardware and the laser rangefinder module).  

Neato XV-11 Wheel Hardware Neato XV-11 Laser Rangefinder Module  Neato XV-11 Laser Rangefinder Module Slip Ring

Heck, he even hacked a Chumby into the Neato XV-11 dustbin (cool hack!).

Chumby hacked into Neato XV-11

Anyway, Hash just recently did a more thorough teardown of the Neato XV-11 Laser Rangefinder circuitry.   Looks like the LRF is using a TI DSP and a Panavision DLIS-2K linear optical sensor (a CMOS camera with a single line of ~2000 pixels).  

Neato XV-11 Laser Rangefinder Circuitry 

Keep up the good work, Hash.  Perhaps we can goad you into writing a Hizook about your exploits some day. 

—Travis Deyle

 They do use a cheap cmos imager that is able to select an Area Of Interest. 

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